In coordination chemistry, a ligand is an ion or molecule that binds to a central metal atom to form a coordination complex. The bonding with the metal involves formal donation of one or more of the ligand's electron pairs; the nature of metal–ligand bonding can range from covalent to ionic. Furthermore, the metal–ligand bond order can range from one to three. Ligands are viewed as Lewis bases, although rare cases are known to involve Lewis acidic "ligands". Metals and metalloids are bound to ligands in all circumstances, although gaseous "naked" metal ions can be generated in a high vacuum. Ligands in a complex dictate the reactivity of the central atom, including ligand substitution rates, the reactivity of the ligands themselves, redox. Ligand selection is a critical consideration in many practical areas, including bioinorganic and medicinal chemistry, homogeneous catalysis, environmental chemistry. Ligands are classified in many ways, including: charge, the identity of the coordinating atom, the number of electrons donated to the metal.
The size of a ligand is indicated by its cone angle. The composition of coordination complexes have been known since the early 1800's, such as Prussian blue and copper vitriol; the key breakthrough occurred when Alfred Werner reconciled isomers. He showed, among other things, that the formulas of many cobalt and chromium compounds can be understood if the metal has six ligands in an octahedral geometry; the first to use the term "ligand" were Alfred Werner and Carl Somiesky, in relation to silicon chemistry. The theory allows one to understand the difference between coordinated and ionic chloride in the cobalt ammine chlorides and to explain many of the inexplicable isomers, he resolved the first coordination complex called hexol into optical isomers, overthrowing the theory that chirality was associated with carbon compounds. In general, ligands are viewed as the metals as electron acceptors; this is because the ligand and central metal are bonded to one another, the ligand is providing both electrons to the bond instead of the metal and ligand each providing one electron.
Bonding is described using the formalisms of molecular orbital theory. The HOMO can be of ligands or metal character. Ligands and metal ions can be ordered in many ways. Metal ions preferentially bind certain ligands. In general,'hard' metal ions prefer weak field ligands, whereas'soft' metal ions prefer strong field ligands. According to the molecular orbital theory, the HOMO of the ligand should have an energy that overlaps with the LUMO of the metal preferential. Metal ions bound to strong-field ligands follow the Aufbau principle, whereas complexes bound to weak-field ligands follow Hund's rule. Binding of the metal with the ligands results in a set of molecular orbitals, where the metal can be identified with a new HOMO and LUMO and a certain ordering of the 5 d-orbitals. In an octahedral environment, the 5 otherwise degenerate d-orbitals split in sets of 2 and 3 orbitals. 3 orbitals of low energy: dxy and dyz 2 of high energy: dz2 and dx2−y2The energy difference between these 2 sets of d-orbitals is called the splitting parameter, Δo.
The magnitude of Δo is determined by the field-strength of the ligand: strong field ligands, by definition, increase Δo more than weak field ligands. Ligands can now be sorted according to the magnitude of Δo; this ordering of ligands is invariable for all metal ions and is called spectrochemical series. For complexes with a tetrahedral surrounding, the d-orbitals again split into two sets, but this time in reverse order. 2 orbitals of low energy: dz2 and dx2−y2 3 orbitals of high energy: dxy and dyzThe energy difference between these 2 sets of d-orbitals is now called Δt. The magnitude of Δt is smaller than for Δo, because in a tetrahedral complex only 4 ligands influence the d-orbitals, whereas in an octahedral complex the d-orbitals are influenced by 6 ligands; when the coordination number is neither octahedral nor tetrahedral, the splitting becomes correspondingly more complex. For the purposes of ranking ligands, the properties of the octahedral complexes and the resulting Δo has been of primary interest.
The arrangement of the d-orbitals on the central atom, has a strong effect on all the properties of the resulting complexes. E.g. the energy differences in the d-orbitals has a strong effect in the optical absorption spectra of metal complexes. It turns out that valence electrons occupying orbitals with significant 3 d-orbital character absorb in the 400–800 nm region of the spectrum; the absorption of light by these electrons can be correlated to the ground state of the metal complex, which reflects the bonding properties of the ligands. The relative change in energy of the d-orbitals as a function of the field-strength of the ligands is described in Tanabe–Sugano diagrams. In cases where the ligand has low energy LUMO, such orbitals participate in the bonding; the metal–ligand bond can be further stabilised by a formal donation of electron density back to the ligand in a process known as back-bonding. In this case a filled
The Death Collector is a 1976 low-budget crime film directed by Ralph De Vito and starring Joseph Cortese, Joe Pesci and Frank Vincent. Sometimes titled Family Enforcer, it was Ralph De Vito's first and last effort as a director and Joe Pesci's first billed appearance in a movie. Pesci and Vincent's performances in the film were met with high critical acclaim. Actor Robert De Niro saw the film and recommended them to director Martin Scorsese for Raging Bull, the start of De Niro's numerous collaborations with Pesci and Vincent; the film follows the progress of Jerry Bolanti a small-time, short tempered crook who becomes an enforcer for the mob. It has the tagline, "If You Liked "The Godfather" & "Dog Day Afternoon," Then This Is Your Kind of Motion Picture." The film became a cult favorite. For around a year in was being screened in the Los Angeles area. Jerry Bolanti, a Mafia-connected hoodlum, is looking for a job. During this uncertain and stressful transitional period, he plays the field to help stay relaxed.
He discovers by accident that he has a talent for debt collecting and intimidation. He decides to pay a visit to a mid-level wiseguy acquaintance and offer up his services, his first task is to collect from a certain Bernie Feldshuh. Before he can deliver the swag to his capo, he is intercepted by Bernie's henchmen, who take back the money and leave him for dead. Jerry returns to Bernie's home while still healing from his gunshot wounds and extracts a moderate amount of retribution. Bernie's response is to hire a top-notch assassin named Marley to take down Jerry as well as the lawyer named Herb Greene who commissioned him to collect on the debt in the first place. An unfortunate secretary becomes collateral damage. Jerry's boss Anthony learns of the deed and sends a man of his own to the score. An unfortunate bodyguard becomes collateral damage, Jerry never does recover the $28,000, his next assignment is to team up with enforcers Joe and Serge to conduct a raid on a shop manager for $40,000 that he may or may not have "owed" to somebody.
But Bernie's newly hired hitman Marley is watching and waiting for an opportunity to take Jerry down. This proves disastrous for the entire operation. After the heist, the trio of gangsters heads over to a hotel room to count out the profits and celebrate a little. While Jerry is downstairs in the hotel restaurant, their secret adversary, assassinates both Serge and Joe, he makes off with the money as well. At this point, Jerry's handler Tony begins accusing him of keeping the loot for himself, he refuses to believe that Jerry could make off with so much money, only to lose it all again. Nobody could be that incompetent. Jerry manages to tease out the contractor's identity from a restaurateur named Spinoza, he terminates his career in a field of tall grass. He receives a call from Gus at the local junk yard. A camper comes in to tell that Jerry might be able to salvage for himself and his live-in girlfriend Paula. Just as things begin looking rosy for Jerry and Paula, he is bushwhacked right in front of the battered red camper by three gun-toting villains.
He dies as a result. The movie ends the same way it began by showing the same two hoodlums in the same automobile dumping yet another body into the same ravine. Only this time, instead of an anonymous corpse, it's young Jerry Bolanti; the mastermind behind this particular hit is shown to be none other than his former boss, Tony. Joseph Cortese as Jerry Bolanti Lou Criscuolo as Anthony Iadavia Joe Pesci as Joe Bobby Alto as Serge Frank Vincent as Bernie Feldshuh Keith Davis as Marley Jack Ramage as Herb Greene Anne Johns as Paula Bob D'Andrea as Ned Victoria Hale as Sally Frank Ammirati as Spinoza Gino Gennaro as Chuck Floyd Levine as Kruger Sal La Pera as Gus Richard Ward as Gunsmith Frank Piazza as Butchy Anthony Manufo as Frank Benino Lorenzo Philip Gonnella as craps dealer Philip Gonnella as craps player The Death Collector on IMDb The New York Times, Oct. 30, 1976 - Bill:'Death Collector,"Violent Professionals' Shown The Death Collector is available for free download at the Internet Archive Death Collector @ THE DEUCE: Grindhouse Cinema Database Family Enforcer at AllMovie
Credit is the trust which allows one party to provide money or resources to another party wherein the second party does not reimburse the first party but promises either to repay or return those resources at a date. In other words, credit is a method of making reciprocity formal enforceable, extensible to a large group of unrelated people; the resources provided may be financial. Credit encompasses any form of deferred payment. Credit is extended by a creditor known as a lender, to a debtor known as a borrower; the term "credit" was first used in English in the 1520s. The term came "from Middle French crédit "belief, trust," from Italian credito, from Latin creditum "a loan, thing entrusted to another," from past participle of credere "to trust, believe"; the commercial meaning of "credit" "was the original one in English" The derivative expression "credit union" was first used in 1881 in American English. Bank-issued credit makes up the largest proportion of credit in existence; the traditional view of banks as intermediaries between savers and borrowers is incorrect.
Modern banking is about credit creation. Credit is made up of two parts, the credit and its corresponding debt, which requires repayment with interest; the majority of the money in the UK economy is created as credit. When a bank issues credit, it writes a negative entry in to the liabilities column of its balance sheet, an equivalent positive figure on the assets column; when the debt is repaid, the credit and debt are canceled, the money disappears from the economy. Meanwhile, the debtor receives a positive cash balance, but an equivalent negative liability to be repaid to the bank over the duration. Most of the credit created goes into the purchase of land and property, creating inflation in those markets, a major driver of the economic cycle; when a bank creates credit, it owes the money to itself. If a bank issues too much bad credit, the bank will become insolvent; that the bank never had the money to lend in the first place is immaterial - the banking license affords banks to create credit - what matters is that a bank's total assets are greater than its total liabilities and that it is holding sufficient liquid assets - such as cash - to meet its obligations to its debtors.
If it fails to do this it risks bankruptcy. There are two main forms of private credit created by banks. To reduce their exposure to the risk of not getting their money back, banks will tend to issue large credit sums to those deemed credit-worthy, to require collateral. In this instance, the bank uses sale of the collateral to reduce its liabilities. Examples of secured credit include consumer mortgages used to buy houses, etc. and PCP credit agreements for automobile purchases. Movements of financial capital are dependent on either credit or equity transfers; the global credit market is three times the size of global equity. Credit is in turn dependent on the reputation or creditworthiness of the entity which takes responsibility for the funds. Credit is traded in financial markets; the purest form is the credit default swap market, a traded market in credit insurance. A credit default swap represents the price at which two parties exchange this risk – the protection seller takes the risk of default of the credit in return for a payment denoted in basis points of the notional amount to be referenced, while the protection buyer pays this premium and in the case of default of the underlying, delivers this receivable to the protection seller and receives from the seller the paramount.
There are many types of credit, including but not limited to bank credit, consumer credit, investment credit, international credit, public credit and real estate. In commercial trade, the term "trade credit" refers to the approval of delayed payment for purchased goods. Credit is sometimes not granted to a buyer who has financial difficulty. Companies offer trade credit to their customers as part of terms of a purchase agreement. Organizations that offer credit to their customers employ a credit manager. Consumer credit can be defined as "money, goods or services provided to an individual in the absence of immediate payment". Common forms of consumer credit include credit cards, store cards, motor vehicle finance, personal loans, consumer lines of credit, payday loans, retail loans and mortgages; this is a broad definition of consumer credit and corresponds with the Bank of England's definition of "Lending to individuals". Given the size and nature of the mortgage market, many observers classify mortgage lending as a separate category of personal borrowing, con